Preparation of guanidine salt



Patented Jan. 9, 1951 PREPARATION OF GUANIDINE SALT Nat H. Marsh, Noroton Heights, Conn., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application November 14, 1949, Serial No. 127,254

2 Claims.

This invention relates to the synthesis of guanidine values by reacting urea with hydrogen sulfide.

It is an object of the present invention to prepare guanidine values by heating the above named inexpensive raw materials under pressure. (By guanidine values is meant guanidine in combined form.) Additional objects will be apparent from the discussion hereinafter.

The following example illustrates without limiting the invention.

Example Into a 300-00. rocker type autoclave there is introduced one mol of urea. The autoclave is then closed and 1 mol of hydrogen sulfide is introduced into it from a transfer bomb. The autoclave is sealed and heated to a temperature of 250 C. under the autogenously developed pressure for four hours. At the end of this period the vessel is cooled, the pressure released, and guanidine values (present as the thiocyanate) extracted by the following procedure. The reaction mass is first extracted with alcohol to remove alcohol soluble materials. The residue is then extracted with cold water and filtered if necessary to remove melamine and other insolubles. The filtrate contains guanidine thiocyanate as well as ammonium thiocyanate, and the guanidine may be precipitated as the sparingly solu ole nitrate by the addition of a soluble nitrate, such as ammonium nitrate.

While the preferred mol ratio of hydrogen batch process, in which event the pressure range suitable is 200 to 20,000 p. s. i. The reaction time suitable will vary with the temperature and pressure, and will, of course, be preferably reduced under conditions of high temperature and. pressure but lengthened under conditions of low temperature and low pressure. At a temperature and pressure of 220 C. and 1000 p. s. i., the preferred reaction period is about 360 minutes. At high conditions of temperature and pressure, such as 400 C. and 2000 p. s. i., the reaction period may be reduced to minutes and even less.

The preferred temperature range is 240-260 C., and the preferred pressure range is 1000-2000 p. s. 1.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. The method of preparing guanidine thiocyanate which includes the steps of heating urea and hydrogen sulfide in a closed reaction zone at a temperature within the range 210-450 C. at a pressure of at least 200 p. s. i., and recovering the thus-formed guanidine values.

2. The method of preparing a guanidine salt which includes the steps of heating urea and hydrogen sulfide in a closed reaction zone at a temperature within the range 240-260 C. and at a pressure within the range 1000-2000 p. s. i., whereby a reaction mass containing guanidine as the thiocyanate is formed, and recovering the said guanidine values.

NAT H. MARSH.

No references cited. 

1. THE METHOD OF PREPARING GUANIDINE THIOCYANATE WHICH INCLUDES THE STEPS OF HEATING UREA AND HYDROGEN SULFIDE IN A CLOSED REACTION ZONE AT A TEMPERATURE WITHIN THE RANGE 210*-450* C. AT A PRESSURE OF AT LEAST 200 P. S. I., AND RECOVERING THE THUS-FORMED GUANIDINE VALUES. 